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For biomedical and textile applications, the comfort of the user will be enhanced if the electronic circuits are not only flexible but also elastic. This letter reveals a simple mouldedinterconnect-device technology for the construction of elastic point-to-point interconnections, based on 2-D spring-shaped metallic tracks, which are embedded in a highly elastic silicone film. Metal interconnections of 3-cm long were constructed with an initial resistance of about 3 Ω, which did not significantly increase (< 5%) when stretched. A stretchability above 100% in one direction has been demonstrated.

This paper presents the design and implementation of an advanced system on flexible and stretchable technology. The technology platform consists of a matrix of flexible non-stretchable functional islands linked together by a net of elastic interconnections. Several technologies have been developed and tested in the design of simplified demonstrators before studying the design of an advanced system. The target system is a wireless battery charger which supplies power and supports bidirectional data transfer during recharge. The system is intended to serve as a general purpose platform for biomedical parameter monitoring and the design is focused on the embedding in clothes.

In order to fit human body, flexibility, or even better stretchability is requested for biomedical systems like implants or smart clothes. A stretchable electronic technology has been developed. This can provide highly stretchable interconnections fully compatible with PCB technologies. In order to prove the feasibility of complex biomedical systems like inner body implants or wearable systems, a variety of stretchable systems has been designed from sensor to power source systems.

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In this work, the design of flexible and stretchable interconnections is presented. These interconnections are done by embedding sinuous electroplated metallic wires in a stretchable substrate material. A silicone material was chosen as substrate because of its low stiffness and high elongation before break. Common metal conductors used in the electronic industry have very limited elastic ranges; therefore a metallization design is crucial to allow stretchability of the conductors going up to 100%.Different configurations were simulated and compared among them and based on these results, a horseshoe like shape was suggested. This design allows a large deformation with the minimum stress concentration. Moreover, the damage in the metal is significantly reduced by applying narrow metallization schemes. In this way, each conductor track has been split in four parallel lines of 15 ptm and 15 ptm space in order to improve the mechanical performance without limiting the electrical characteristics. Compared with the single copper or gold trace, the calculated stress was reduced up to 10 times.

An MID (Moulded Interconnect Device) technology was developed for the production of elastic electronic interconnections. The stretchability is obtained using tortuous horseshoe shaped metallic wiring, embedded in a matrix of PDMS (poly dimethyl siloxane). In this way stretchable interconnects have been realized, consisting of 4 micron thick gold wires, embedded in 250 − 500 μm thick silicone material. . Stretchable interconnections, realised with this technology, have a maximum stretchability above 100%, with a stable resistivity of about 1.5 Ω per running cm for a track width of 100μm. A first simple operating stretchable electronic circuit has been fabricated, consisting of a blue LED driven by stretchable wiring. The technology is under development for use in biomedical applications in the first place, but has potential to be extended for various other applications like smart textiles, robotic skins, etc.

For user comfort reasons, electronic circuits for implantation in the human body or for use as smart clothes should ideally be soft, stretchable and elastic. In this contribution the results of an MID (Molded Interconnect Device) technology will be presented, showing the feasibility of functional stretchable electronic circuits. In the developed technology rigid or flexible standard components are interconnected by meander shaped metallic wires and embedded by molding in a stretchable substrate polymer. Several technologies have been developed to this purpose, which combine low cost and good reliability under mechanical strain. In this way reliable stretchability of the circuits above 100% has been demonstrated. Enhanced reliability has been reached using an additional conductive polymer layer.